Erwinia amylovora modifies phenolic profiles of susceptible and resistant apple through its type III secretion system.

Fire blight is a disease affecting Maloideae caused by the necrogenic bacterium Erwinia amylovora, which requires the type III protein secretion system (TTSS) for pathogenicity. Profiles of methanol-extractable leaf phenolics of two apple (Malus x domestica) genotypes with contrasting susceptibility to this disease were analyzed by HPLC after infection. Some qualitative differences were recorded between the constitutive compositions of the two genotypes but in both of them dihydrochalcones accounted for more than 90% of total phenolics.

Identification of a major QTL together with several minor additive or epistatic QTLs for resistance to fire blight in apple in two related progenies.

Although fire blight, caused by the bacterium Erwinia amylovora, is one of the most destructive diseases of apple (Malus x domestica) worldwide, no major, qualitative gene for resistance to this disease has been identified to date in apple. We conducted a quantitative trait locus (QTL) analysis in two F(1) progenies derived from crosses between the cultivars Fiesta and either Discovery or Prima. Both progenies were inoculated in the greenhouse with the same strain of E.